The present invention relates to a fluorescent display device of an internal fixing structure in which leads of a control electrode are directly connected to the control electrode terminals provided on a substrate.
A fluorescent display device generally comprises a phosphor coated anode functioning as a display pattern, a cathode for emitting electrons and a control electrode for accelerating and controlling the electrons emitted from the cathode. These electrodes are held in a high vacuum envelope,
As a structure for providing the electrodes in the envelope, there is known an internal fixing structure in the art. As shown in FIG. 2, this structure includes terminals 101 provided on a substrate 100 as a part of the envelope, a control electrode 102, and leads 103 provided on an outer periphery of the control electrode 102 and connected to the terminal 101. The leads 103 are connected and fixed to the terminals 101 by a conductive adhesive agent. The control electrode 102 is fixed to the substrate 100 spaced apart from the substrate 100 by means of the leads 103 so that the control electrode may be arranged above a display area 104 of the substrate 100. The leads 103 serve as a spacer for locating the control electrode 102 at a position spaced by a predetermined distance from the substrate 100. The leads 103 also serve as a lead wire to apply control voltage to the control electrode 102 through the terminals 101. In the outer peripheral edge of the substrate 100, anode terminals 105 are arranged in parallel at a regular interval to which lead-in wires 106 are connected and led out of the vacuum envelope.
In the conventional fluorescent display device of an internal fixing structure, the terminals 101 for the control electrode 102 and the leads 103 for the terminals 101 and the control electrode 102 are arranged in the inside of the substrate 100 where the anode terminals 105 are arranged. The display area 104 is located in a further inner area thereof. Thus, a distance L from the outer periphery of the substrate 100 on the side of the lead-in wires 106 to the outer periphery of the display area 104 is long and that the area of the display area 104 is small relative to that of the substrate 100.
For example, In case where the dimension of the substrate is 40 mm.times.100 mm, and the thickness of a side plate mounted on the outer periphery of the substrate is 2.35 mm, the distance n is 6.5 mm. This means that the dimension of the display area is 27 mm.times.72 mm, and the display area is only 48.6% of the dimension of the substrate.